Non-native Species Introductions Can Lead to New Illnesses

By Jenny Finfera
Columbus Ecological Services Field Office

Mention invasive species, and many of us think of Asian carp, zebra mussels or perhaps a plant like Asian bittersweet. But there are other, less recognized examples. Consider West Nile disease, caused by a non-native virus that was first detected in the U.S. in 1999. The virus is believed to have arrived here by the inadvertent transport of an infected mosquito.

White-nose syndrome is another example of how non-native organisms can cause the emergence of diseases new to the United States. White-nose syndrome was first detected in bats in New York, in 2006, and is characterized by the growth of fungal hyphae on the skin of bats. The fungal growths resemble white fuzz on the wings and muzzles of infected bats, giving the disease its name. The fungus causing white-nose syndrome is called Geomyces destructans and had not been identified in North America prior to 2006.

This fungus has been found in bats in Europe, but the bat species there do not suffer the same high rates of mortality. However, the impact of white-nose syndrome on North American bats has been dramatic – the disease has killed an estimated 5.5 million cave-dwelling bats in the eastern half of the country since it was discovered. Mortality in affected hibernacula can reach 90 percent in some species.

Both of the West Nile Virus and Geomyces destructans are non-native organisms. They have each had a significant impact on ecosystems. West Nile virus has been detected in over 200 bird species with the deaths of over 40,000 individual birds. White-nose syndrome has been associated with nine species of bats here in North America. As the pathogen spreads, additional bat species may be affected.

Since both of the West Nile Virus and Geomyces destructans are new to North America, our native species have not developed an immune system response to these pathogens, making the illnesses highly virulent. While the impacts to birds from West Nile have lessened, the spread of white-nose syndrome has continued to threaten North American bat species as it spreads across the country. The population declines have been so significant that there is concern that additional bats species may need to be listed under the Endangered Species Act.

While both the fungus that causes white-nose syndrome and the virus that causes West Nile are small invasive species, there are other larger invasive species that also have a significant impact on native ecosystems. National Invasive Species Awareness Week focuses on this in early March, offering an opportunity to look at the threats posed by invasive species and the everyday actions individuals can take to help prevent the introduction and spread of non-native species.